[love_da_ocean]

How strong of lighting does a clam need?

[Ninong]

Hi love_da_ocean, welcome to Reefland!

Daniel Knop is a recognized expert on Tridacnid clams. In this article he discusses lighting requirements: http://www.animalnetwork.com/fish2/a...ll/default.asp

[Poseidon]

Ninong you have all the coolest Links....

I wish I had the memory you do, I bet you remember almost every article you have read, and more importantly where you read it!!!!

Mike

[Rook]

I read that article pointed out above by Knop. I noticed it was a few years old. Is the information in this article still considered good information? Specifically, Knop talked about kelvin ratings for clams and suggested that between 5-10K lighting to be best for clams, and that 20K lighting would not be natural and less adequate. Is this still accurate, and if so, does that also mean that adding actinic supplimentation to a 10K MH lamp would put the lighting at undesirable kelvin ratings for clams?

Also he spoke about the use of carbon with clams and the side effects of removing good nutrients and chemicals and with changing the light spectrum. What is everyone's opinion on this topic?

[Ninong]

Originally Posted by Rook

I read that article pointed out above by Knop. I noticed it was a few years old. Is the information in this article still considered good information?

Yes.

Specifically, Knop talked about kelvin ratings for clams and suggested that between 5-10K lighting to be best for clams, and that 20K lighting would not be natural and less adequate.

This is Daniel Knop's explanation: Under natural conditions, most of the smaller giant clam species inhabit the shallow, strongly illuminated portions of the reef. The small T. crocea, in particular, lives in extremely shallow water and is rarely found at greater depths, while T. maxima is also found in shallow water between 10 and 15 meters (30 to 50 feet) in depth — usually not deeper. The same holds true for T. squamosa. At 15 meters (50 feet) in depth, Kelvin (K) values average 10,000 K. If we keep giant clams in aquariums with lamps that produce light in the 20,000 K range, we are keeping them under conditions that, in nature, would be found at depths of 20 to 50 meters (65 to over 160 feet) — depths at which giant clams cannot survive (except the extremely rare species T. tevoroa, which can still be found as deep as 30 meters). For this reason, I strongly suggest that lamps that produce light with values over 10,000 K not be used for giant clams.

Is this still accurate, and if so, does that also mean that adding actinic supplimentation to a 10K MH lamp would put the lighting at undesirable kelvin ratings for clams?

If you are setting up a tank for Tridacna crocea, and nothing else, then 6500K would be ideal. If you intend to keep other Tridacnids besides T. crocea, then 10,000K would be better (IMO) but either 6500K or 10,000K would be fine. Supplemental lighting (actinic fluorescents or 20,000K metal halides) simply adds additional photons in the shorter wavelengths.

Also he spoke about the use of carbon with clams and the side effects of removing good nutrients and chemicals and with changing the light spectrum. What is everyone's opinion on this topic?

I follow Knop's recommendation. I run carbon 24/7 and change it once a month. In my mind the benefits of using carbon outweight the negatives of what desirable nutrients it might remove. This is what Daniel Knop said he does: This is, of course, not an argument against the use of activated carbon in the clam tank. But we change the carbon once a month in clam tanks and use it in moderate amounts, so no sudden changes of water chemistry or the spectral light composition will occur.

He is saying that sudden changes to either water chemistry or spectral light composition can be harmful. Such an example would be someone who waits for the water to appear yellowish before they suddenly run a liter of carbon for a few days to clear things up and then wait another six months before doing it again. I don't believe his admonition applies to people who choose to run carbon for a few days once a month and it certainly doesn't apply to people who run it in moderation 24/7 because that's what he does himself. Some people never run carbon because they are concerned that it removes iodine (iodide/iodate) and other nutrients that they would rather not remove -- note his reference to zeniids.

[Rook]

Thank you for the clarification. Just to make sure I am understanding the point about the light wavelengths;

So, If I have a mixed reef with mixed clams (maxima, crocea, squamosa + coral and other inverts) and I have a 10K metal halide and VHO actinic supplementation, the overall light, while the color appears more blue to me, still contains 10K wavelengths and other spectrums from the VHO. The mixing of the VHO with the MH does not change the overall spectrum of the wavelengths. So, the addtion of the VHO is not "hurting" the clams by altering the wavelengths?

[Rook]

Someone before, somewhere had a description of the intensity of different types of lighting, (MH vs VHO vs PC) at different depths in a tank. Does anyone remember that and know where I can find it?

I have "good" lighting IMO, but I have had many ask me about having clams in under VHO and PC, at shallow depths and thought that reference would be good.

What are your thoughts about PC and VHO for clams, if at shallow depths? For example, what if a person had a 10 gallon tank? Assume for arguments sake that the water quality and stability are pristine and the only point in question is whether the lighting, using PC or VHO is adequate?

I thought that "article" showed the intensity of PC and VHO compared to MH at variouse depths and wanted to see if PC and VHO really have enough intensity at those shallow depths for clams.

[Ninong]

Originally Posted by Rook

Thank you for the clarification. Just to make sure I am understanding the point about the light wavelengths;

So, If I have a mixed reef with mixed clams (maxima, crocea, squamosa + coral and other inverts) and I have a 10K metal halide and VHO actinic supplementation, the overall light, while the color appears more blue to me, still contains 10K wavelengths and other spectrums from the VHO. The mixing of the VHO with the MH does not change the overall spectrum of the wavelengths. So, the addtion of the VHO is not "hurting" the clams by altering the wavelengths?

Correct. It's like having five quarters, three dimes and a penny and someone gives you two additional pennies. You still have the same quantity of quarters and dimes. The only thing that has changed is that you now have more pennies.



P.S. -- The addition of the VHO is not "hurting" anything because it is not altering the wavelengths at all; it is simply adding additional "quantity" (photons) in certain wavelengths, which is something that we "see" thanks to our particular visual physiology. We "see" only a very small part of the electromagnetic field and our perception within the range of "visual light" is more acute in the yellow/green range, as would be expected of diurnal bipedal primates with binocular vision that have done most of their hunting in the sunlight for the past couple of million years. If we were still nocturnal, like cats, we would probably perceive colors differently and have more sensitive night vision. The various pigments that are responsible for assisting photosysthesis in the symbiotic zooxanthellae each have their own particular "visual" sensitivities and are more receptive to certain wavelengths than others and since the symbiotic dinoflagellates are primary producers that have evolved to utilize sunlight (energy) in production, they are more specialized in their reception than consumers like us that just use sunlight to see where we are going so that we can find something to consume.

[Rook]

Thanks again for the claifications. That really helps.

Another question, the true color of clams can really only be seen from above. Knop explains that the reason for this is because the light comes from above, and the true color is seen from the direction of the light source. What if instead of using a clam tank design like Knop's or Barry's, I placed a few lights at the very front of the tank at the water surface and pointed the light directly at the clam? Would this help for the clam's color to be seen more adequately from the front? Would it matter on the light for this purpose, assuming you still use 10K MH for the main light? Like using some kind of LED spot light?

[Ninong]

The color that we perceive when we look at a clam's mantle is more of an illusion than a physical color. I hope I can leave it at that because an explanation would take several pages.

Here is a neat experiment for you: After all of your lights are off at night, take a very bright flashlight and shine it on the clam through the front glass of the tank being careful to hold the flashlight as close to your head as possible (hold it against your ear) so that you are viewing the clam in the same path as the flashlight is illuminating it. The colors that you see will be very similar to what you see when you look down on the clam from the top of the tank with the tank's lights on. There will be slight differences caused by the fact that the iridophores in the mantle are pointed up and will absorb light deeper if it comes from above rather than from the side. Don't do this too often or for too long a period of time as it is unsettling to the clam.

I don't think it is ever a good idea to try anything that differs drastically from what the animal (clam, coral, etc.) would experience in its natural environment. Some folks do try to mimic the rising and setting sun in very elaborate, very expensive lighting systems over very large, very expensive tanks but even they regulate this omnidirectional lighting so that it is directly overhead for most of the photoperiod. If the main metal halide lighting is directly overhead, I don't think there would be any problems in having some supplemental actinic lighting from the front of the canopy that is angled slightly towards the reef's main structure. I have seen this done as a way to get the actinic lighting to cover more of the tank when it is positioned in front of the main lighting.

If you position your metal halide lighting so that it is continuously striking the reef structure (clams, corals, etc.) from an angle, the photosynthetic animals will re-orient themselves to expose the maximum surface to the direction of the light source. I wouldn't recommend it.

[Rook]

I ask because I have noticed the color difference with a flashlight before. I regularly check my tank at night with a flashlight. Just wondering if it would work or not.

Thanks for the help.